Short term change in relative humidity during the festival of Diwali in India

•Changes in RH during Diwali have been examined over a period of 13 years in India.•Increase in RH even in the absence of transport of humid air has been observed.•The RH levels were found to be exceeding the ambient levels during night.•The RH levels were found to be lying below the ambient levels during morning hours.•Increase in viral infections is observed.

The changes in humidity levels during the Diwali festivities have been examined over a period of 13 years at three Indian metro cities: Ahmedabad, New Delhi and Kolkata. A small short term increase in relative humidity even in the absence of transport of humid air from Arabian Sea and Bay of Bengal has been observed. The relative humidity levels were found to be exceeding the ambient levels during night and lying below the ambient levels during morning hours, indicating an increase in the survival rates of viruses responsible for the transmission of viral infections, as well as triggering immune-mediated illnesses such as asthma during Diwali.